> He wanted to write a Unix-like OS but for mainframes Historically that was a very common thing, numerous examples from the 70s and 80s. Princeton's 1970s por

> He wanted to write a Unix-like OS but for mainframes Historically that was a very common thing, numerous examples from the 70s and 80s. Princeton's 1970s port (which Eric Schmidt worked on) that evolved into Amdahl UTS; AT&T's early 1980s port which run on top of TSS/370; Nixdorf ported Coherent from the PC to run on top of DOS/VS (IBM mainframe DOS/360, unrelated to MS-DOS/PC-DOS) and sold that as PWS/VSE-AF. There was also VM/IX, IX/370, AIX/370, AIX/ESA, MVS OpenEdition (now z/OS Unix System Services) and its VM/CMS equivalent (originally also called OpenEdition, now z/VM OpenExtensions). And nowadays z/Linux is big, and there was also Sine Nomine Associates' OpenSolaris port (which sadly went nowhere). Writing a Unix subsystem which runs on top of MVS 3.8J (or DOS/VS, or VM/370, or MTS, or MUSIC, etc) would be interesting. Utterly pointless and practically irrelevant, but still interesting. But, since stuff like OS/380 and PDOS is just a hobby, who cares if it has a point or practical relevance? It has a point so long as somebody enjoys it.